1. Technical Field
The present invention relates generally to detection of defects in railroad wheels. More particularly, this invention relates to improved electromagnetic acoustic testing of wheels for defects.
2. Related Art
In the railroad and related industries, wheel defects and/or extreme wear are a major cause of derailments leading to property loss and loss of life. Detection of defects and wear before a tragedy occurs, therefore, has become indispensable. An ideal device must address the requirements of: longevity, accuracy, reliability, quickness and expense. Unfortunately, no fully satisfactory automated means capable of meeting these requirements for testing railroad wheels on rolling stock presently exists.
U.S. Pat. No. 3,812,708 to Cowan et al. teaches the use of ultrasonic transducers enclosed in a flexible fluid-filled boot and positioned adjacent to a thin vertical rail in a test zone. In this device, the liquid-filled urethane boot suffers from fragility since it is susceptible to small cuts that release the liquid. In addition, the system is inaccurate because it produces a high rate of false positive indications. See also Scanning Systems, Inc. xe2x80x9cWheelCracks? Wheelfacts? WheelFAX!xe2x80x9d brochure.
German document DE 3218453A1 to Salzberger et al. discloses a device using electromagnetic acoustic transducers (EMATs). This system reduces the number of false positives, but is inflexible because it can only test wheels having tightly controlled wear profiles. This system also suffers from the use of electromagnets, which create an upper limit on train length due to overheating in the transducer. Finally this system is incapable of real time on-line signal processing necessary in heavy traffic situations.
National Institute of Standards and Technology, Report No. 22, Tread Crack Detection in Railroad Wheels: An Ultrasonic System Using EMATs, by Schramm et. al., discloses improvements to the Salzberger et al. device. Shramm et al. introduce membrane sensing switches and conforming transducers to expand wheel profile and size compatibility and suggest improvements in signal processing. As indicated in that document, there are a number of shortcomings of this device. Problems include corrosion and a lack of a workable mounting mechanism for the sensor. Due to a lack of a mounting system, the device requires a lot of attention by a user and is unreliable. It is also expensive to use because the transducer is free to move around and, hence, susceptible to breakage. Another problem with the system is noise created by the traction system of the locomotive, which creates false positive indications.
In view of the foregoing there is a need in the art for a wheel inspection system that exhibits: longevity, accuracy, reliability, quickness, cost-effectiveness and user independence.
In a first general aspect of the invention is provided a wheel inspection system having: an electromagnetic acoustic transducer having a transmit coil to propagate an ultrasonic wave into a wheel and a receiving coil to receive an ultrasonic surface wave from the wheel; a radio frequency generator for exciting the electromagnetic acoustic transducer and producing an ultrasonic wave in the wheel; a computer control unit connected to and communicating with the radio frequency generator and the electromagnetic acoustic transducer; a data acquisition unit connected to and in communication with the computer control unit and the electromagnetic acoustic transducer assembly for determining defects in the wheel; and a noise removing system to remove noise from the data. This aspect provides a system capable of accurately, quickly and reliably detecting defects in a wheel.
In a second general aspect of the invention is provided A detection head for an electromagnetic acoustic transducer wheel inspection system, the detection head having: a housing for holding transducer components, the detection head including a transducer pocket and a magnet pocket; a removable magnet assembly for removably mounting a magnet to the magnet pocket; and a removable transducer assembly for removably mounting a coil assembly of the transducer to the transducer pocket.
In a third general aspect of the invention is provided a wheel inspection system having a sensor for receiving signals sent through a wheel; and a data acquisition unit connected to and in communication with the sensor, the data acquisition unit including a neural network, to determine the presence of defects in the wheel, for each sensor.
A fourth general aspect of the invention provides a wheel inspection system having means for detecting defects in a wheel; and means for pivotally mounting the detecting means to a wheel supporting surface such that the detecting means may pivot about least two axes.
The foregoing and other features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention.